The last working versions for me were xserver-xorg-core_1.16.2.901-1ubuntu4 and xserver-xorg-video-radeon_7.5.0-1ubuntu1
1.17 introduced the problem.
The last working versions for me were xserver- xorg-core_ 1.16.2. 901-1ubuntu4 and xserver- xorg-video- radeon_ 7.5.0-1ubuntu1
1.17 introduced the problem.